Safety interlock for gas-filled switch mechanisms



Sept. 14, 1965 J. E. HARDER ETAL 3,206,583"

SAFETY INTERLOCK FOR GAS-FILLED SWITCH MECHANISMS Filed Sept. 19, 1961 2 Sheets-Sheet 1 Fig.l.

INVENTORS John E.Horder and Edward H. Waters. saw/X AT TOR N EY Sept. 14, 1965 J. E. HARDER ETAL 3,206,583

SAFETY INTERLOCK FOR GAS-FILLED SWITCH MECHANISMS Filed Sept. 19, 1961 2 Sheets-Sheet 2 United States Patent 3,206,583 SAFETY LNTERLOCK FOR GAS-FILLED SWITCH MECHANISMS John E. Harder, Richland Township, Monroe County, and Edward H. Waters, Bloomington, Ind., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Sept. 19, 1961, Ser. No. 139,083 Claims. (Cl. 200148) This invention relates generally to gas-filled switch mechanisms and relates more particularly to a gas loss safety interlock and gas loss indicator therf-or.

In gas-filled distribution protective equipment, it is important that there be some indication on the exterior of the switch to indicate the occurrence of a gas loss to warn an operator or maintenance personnel that the gas within the device is insufficient for arc interruption purposes.

Accordingly, it is an object of this invention to provide a simple gas loss safety lock and indication mechanism for use with gas-filled switches.

It is another object of this invention to provide in a gasdilled switch, an indication of gas loss by means of an interlock device on the operating handle of the switch, thus eliminating the necessity for an additional opening in the gas-filled tank.

It is yet another object of this invention to provide in a gas-filled switch, a gas loss safety interlock device which prevents opening of the switch in the event of a gas loss, but permits a contact closing operation to proceed even though gas is lost so that the primary aim of service continuity is maintained.

Another object of this invention is to provide in a gas-filled switch, a gas loss safety interlock device re-' quining only a small amount of energy expenditure in its operation, to facilitate the use of sensitive pressure sensing devices with a considerable factor of safety.

It is another object of this invention to provide in a gas-filled switch, a gas loss safety interlock device entirely enclosed within the gas-filled tank and operable to prevent operation of the contact operating mechanism, with indication of gas loss provided by the immobility of the operating handle externally of the tank.

These and other objects will be better understood from the following description taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is an elevational view, taken in section, of a gas-filled sectionalizer, including the gas loss safety interlock device of the present invention;

FIG. 2 is a top plan view of the operating mechanism of the sectionalizer of FIG. 1, showing the gas loss lock device of this invention associated therewith;

FIG. 3 is an elevational view, taken partly in section, of the operating mechanism of FIG. 2; and

FIG. 4 is a side elevational view of the gas loss lock device shown in FIG. 2.

Generally stated, the present invention provides in the tank of a gas-filled switch a pin carried by a sealed bellows and disposed adjacent the contact operating mechanism for movement into the path of the operating mechanism as the bellows expands in response to change in relative density between the gas in the tank and the gas in the bellows, to thus prevent operation of the operating mechanism. Initially, the differential in density between the gas in the tank proper and the gas within the sealed bellows is such as to normally compress the bellows to maintain the pin out of locking engagement with the operating mechanism. Thereafter, if either the tank or bellows should leak, the bellows expands to insert the pin into locking engagement with the opera-ting mechanism. Thus, gas loss is indicated to an operator when the handle 3,206,583 Patented Sept. 14, 1965 mechanism of the switch resists a contact separation operation by the operator.

By utilizing bellows means as the loss of gas indicator in the gas loss lock device, there is provided a highly sensitive gas density responsive device capable of accurately detecting gas loss from the tank enclosing the switch mechanism. At the same time, by enclosing the bellows entirely within the tank, and establishig the basis of operation of the gas loss lock device upon density differential between the gas in the bellows and the gas in the tank proper, rather than upon the relative deviation of the pressure within the tank with respect to a predetermined fixed pressure or atmospheric pressure, the gas loss lock device is rendered insensitive to change in pressure within the tank caused solely by temperature changes.

In gas-filled switches, such as sectionalizers, it is supposed that the dielectric strength or the interrupting ability of the gas, such as SP is a function principally of the density of the gas. If, for instance, an amount of gas is sealed in a closed constant volume container, the pressure of this gas will vary roughly with the absolute temperature. It has been determined for applications expected within the continental United States that with a tank charged to a gauge pressure of 30 p.s.i.g. at room temperature and roughly sea level pressure, it would be altogether feasible that the gauge pressure within this tank might vary from about 19 p.s.i.g. .to around 40 p.s.i.g. without any change in density of the gas on the inside of the tank. It is proposed that the gas loss lock device to protect against operation of the switch on loss of gas would be opera-ted by a sealed metallic bellows into which the gas would be sealed. This gas should have the same pressure temperature relation for constant volume as the gas used in the interrupter chamber. Thus, when the temperature rose, the pressure in this bellows would rise at the same rate as the pressure in the interrupter tank, and thus no net force or motion would occur in the bellows system. If, however, the pressure in the bellows increased with respect to the pressure in the tank this would mean that either the temperature of the bellows was rising with respect to the temperature in the tank, which would be unlikely since temperature changes are normally slow, or that gas was leaking out of the tank.

In an alternate embodiment, the bellows would be filled with the same gas as the interrupter chamber and at the same pressure. This would have the advantage that if the bellows were to spring .a leak there would be no contamination of the arc interrupting gas.

Thus, this bellows arrangement sealed entirely in the gas space of the interrupter chamber gives an indication of gas density in the interrupter chamber or a change in gas density in the interrupter chamber, and at the same time is insensitive to pressure changes within the tank resulting from slow changes in temperature.

Referring to FIG. 1 of the drawing, there is disclosed a gas-filled sectionalizer 10 comprising a pressure vessel or tank 11 having an externally. mounted operating handle mechanism 12 at the bottom thereof, and a pair of bushings 13 (only one shown) projecting from the top thereof. The tank 11 is hermetically sealed and contains therein suitable arc interrupting gas, such as sulfur hexafluoride. Mounted within the tank is an operating mechanism 14 connected to operate a contact mechanism 15 in response to the operation of an integrator mechanism 16, or, in response to the operation of the handle mechanism 12.

Thus, the operating mechanism 14 operates the contacts 15 in a sectionalizing mode as controlled by integrator 16, while operation of the handle mechanism 12 operates the operating mechanism to control the contacts 15 in a switching mode.

The gas-filled sectionalizer generally, and the operating mechanism 14 in particular, are disclosed and claimed in copending application Serial No. 139,084, filed September 19, 1961, by John E. Harder.

The integrator mechanism 16 with the associated solenoid 17 is disclosed and claimed in copending application Serial No. 139,195, filed September 19, 1961, by A. R. Harm and W. D. Wagner, which issued December 10, 1963, as U.S. Patent 3,114,021, and is assigned to the same assignee as the present application.

Although this invention is particularly disclosed herein as incorporated in a gas-filled sectionalizer of the type disclosed in copending application Serial No. 139,084, previously mentioned, it is to be understood that the invention is not limited in use to this particular gas sectionalizer, but is useful with other types of switches generally, where it is desired to prevent separation operation of contacts within a gas-filled tank whenever a gas loss occurs.

The operating mechanism 14, as fully described in detail in the aforementioned application Serial No. 139,084, comprises a lever system 18, which includes a pair of levers 19, 20 pivotally connected to each other by a pivot pin 21 and resiliently biased into predetermined normal alignment with respect to each other about pin 21 by means of a spring mechanism carried by the levers 19 and 20, and generally indicated at 22. The lever system 18 is pivoted at one end about a pivot 23 on a support frame 24 so that the free end of the system 18 may move from either one of a pair of latch means 25, 26 to the other, which latch means 25, 26 are fixedly spaced on the support frame 24 so as to normally individually engage the free end of lever 20 of the lever system 18. The operating handle mechanism 12, FIG. 1, is connected to the lever 19 adjacent the pivot 23 by means of a connector mechanism 27 extending through an aperture 28 in tank 11, the aperture being hermetically sealed by a bellows means 29 connected at the upper end to a rod 30 in the connector mechanism, and being connected at the lower end in sealed relationship with aperture 28 in tank 11.

In operation, the downward movement of the handle mechanism 12 rotates the lever system 18 clockwise about pivot pin 23 against the holding force of latch 25, whereupon the spring biasing mechanism 22 yields resiliently to permit buckling of the levers 19 and 20 with respect to each other about pivot 21, thus charging the spring, and at the same time shortening the effective length of the lever system 18 between pivot 23 and latch 25 to ultimately release the lever system 18 from the latch by sliding disengagement therewith. After disengagement occurs, the charged spring system 22 snaps lever 20 into alignment with lever 19, now in the down position, illustrated in broken lines in FIG. 3, to effect snap opening action of the contact means connected to the free end of lever 20 and to propel the free end of the lever system 18 past the lower latch means 26 whereupon the latch 26 holds the lever system 18 in the lower position, holding the contacts in a separated condition. Thereafter, operation of the handle mechanism 12 in the opposite direction effects reverse action of the lever system counterclockwise about pivot 23 to the upper latch 25 with a snap closing action in the same manner as that described in the contact opening operation of the operating mechanism as described above.

In accordance with the present invention, there is provided a gas loss lock mechanism 100 disposed adjacent the operating mechanism 14, and operable in response to gas loss from the tank to insert a stop or pin into the operating mechanism to prevent its operation from the closed contact condition to the open contact condition.

The gas loss lock device 100 comprises a mounting frame 101, a bellows mechanism 102 thereon, and a lock pin 103 carried by the bellows.

The mounting frame 101 is an open-sided bracket frame including a top wall 104, a bottom wall 105, a

back wall 106, and a recessed front wall 107 to which the top wall 104 and bottom wall 105 are fixedly attached 1n any suitable manner. A mounting tab 103 is provided on the front wall for attaching the mounting bracket frame to support plate 24 of the operating mechanism as shown in FIGS. 1 and 2.

The bellows mechanism 102 may be of any suitable type, but is preferably metallic, such as beryllium copper and is mounted between the walls 104, 105 for expansion along an axis parallel to the walls 104, 105 and perpendicularly with respect to support plate 24. The rear of the bellows carries an axially extending filling tube 109 extending through a centrally disposed aperture in rear wall 106, thus serving as a means for fixing the rear of the bellows with respect to the mount 101. The forward end of the bellows carries the lock pin 103 extending axially of the bellows and extending through a centrally disposed aperture in the recessed front wall 107, and extending through a second aperture 110 in the support plate 24, the apertures being aligned along the axis of motion of the bellows so that expansion and contraction of the bellows moves the pin 103 axially into and out of engagement with the end of lever 19 of the operating mechanism 14 as shown in FIG. 3 of the drawing. A limit pin 111 is provided transversely through lock pin 103 for defining the inner limit of motion of pin 103 when the bellows is compressed. The pin 111 also functions to prevent the integrator 16 from opening the sectionalizer automatically as will be described more fully hereinafter.

Initially, the bellows 102 is filled with gas through the filling tube 109. The gas is preferably of the same type as used in the tank 11 as the arc interrupting medium to thus eliminate pressure differential between the gas in the bellows and gas in the tank as may be caused by temperature deviation. The density of the gas within the expanded bellows is less than that of the surrounding area within the tank 11 to effect normal compression of the belows and corresponding withdrawal of pin 103 from the path of motion of lever 19 as it moves clockwise about pin 23.

If a gas loss should occur when the operating mechanism is in the contact closing position as shown in FIG. 3, the density diiterential between the gas in the tank 11 and the bellows 102 will decrease, gradually effecting expansion of the bellows and eventual motion of the pin across the top of lever 19, FIG. 3, whereupon downward motion of the handle will be resisted by the locked mechanism to thus prevent a contact separation operation of the mechanism 14 and indicating to the operator the occurrence of a gas loss from tank 11.

Referring to FIG. 2, it will be seen that the pin 111 will interfere with movement of a trip bar 112 to the left when the bellows 102 is expanded, thereby preventing the integrator 16 from causing automatic tripping of the sectionalizer in the manner described in copending application Serial No. 139,084, previously mentioned. Thus, the sectionalizer is prevented from operating in a sectionalizing mode if there is insutficient gas for interruption in the sectionalizer.

If the gas loss should occur while the contacts 15 are in the open condition, as illustrated in the broken line position of the lever 19 in FIG. 3 and the aligned condition of lever 20 with respect thereto as described above, the pin 103 will move inwardly to engage the side of lever 19 rather than to overlie lever 19 so that the operator may close the contacts without interference from the gas loss lock mechanism. However, after closing, the contacts, the pin 103 will overlie the lever 19 as described above and prevent contact separation operation of the operating mechanism.

If desired, a recess, not shown, may be provided in the side of lever 19 for alignment with the pin 103 when the operating mechanism is in the open position, to prevent closing of the contacts 15 in the event of a gas loss.

If the bellows 102 should leak, the pressure differential between the gas in the tank and the bellows would decrease, eilecting locking of the operating mechanism as described. This feature provides a fail-safe operation of the gas loss lock device.

If desired, a Bourdon tube type gauge or other pressure sensitive device may be substituted for the bellows to move the pin into locking engagement with the operating mechanism.

For the foregoing reasons, it is seen that there is provided a fail-safe gas loss safety interlock device capable of holding the operating mechanism in the contact closed position in response to gas loss from the tank, and which is capable of insensitivity to changes in pressure in the tank resulting from temperature changes.

While there has been shown and described certain preferred embodiment of this invention, it will be obvious to those skilled in the art that it is not so limited but is susceptible of various changes and modifications without departing from the spirit and scope thereof.

We claim as our invention:

1. An enclosed switch, comprising: a sealed tank; an arc interrupting gas disposed in said tank; a switch mounted in said tank and including separable contacts and an operating mechanism for actuating said contacts between open and closed positions; a closed expansible chamber means mounted in said tank adjacent to said operating mechanism; a gas disposed in said chamber having a pressure-temperature relationship for a constant volume of gas substantially the same as that of said gas in said tank; the density of the gas in said chamber being equal to the density of the gas in said tank when the expansible chamber means is normally compressed whereby a predetermined loss of the gas from the tank or a leak of the gas from said chamber will effect expansion of said chamber means independently of said operating mechanism; and means carried by said chamber means for preventing operation of the switch operating mechanism when the chamber is in the expanded condition.

2. An enclosed switch, comprising: a sealed tank; an arc interrupting gas disposed in said tank; a switch mounted in said tank and including separable contacts and operating means for actuating the contacts between open and closed positions; expansible chamber means mounted in said tank adjacent to said operating means; a gas disposed in said chamber having a pressure-temperature relationship for a constant volume of gas substantially the same as that of the gas in said tank; the density of the gas in said chamber being equal to the density of the gas in the tank when the chamber is compressed whereby a predetermined loss of gas from the tank will effect expansion of said chamber means, the forces applied to said contacts by said operating means during opening and closing of the contacts being normally substantially independent of the gas density in said tank; and means actuated by said chamber means and engageable with the operating means for locking engagement therewith to prevent operation of the switch operating mechanism when the chamber is in the expanded condition.

3. An enclosed switch, comprising: a sealed tank; an

arc interrupting gas disposed in said tank and having a predetermined density; switch means in said tank including separable contacts and an operating mechanism operable to apply forces which are normally substantially independent of the gas density in said tank to selectively move said contacts from either one of two operating positions to the other to thereby open and close said contacts respectively; handle means operatively connected to said operating mechanism through a sealed aperture in the tank wall and mounted externally of the tank to manually operate said operating mechanism from either one of said two positions to the other; means in the tank responsive to a predetermined loss of gas from the tank independently of said operating means to prevent operation of the operating mechanism and the external handle means from the contact closing position.

4. An enclosed switch, comprising: a sealed tank; switch means disposed in said tank, an arc interrupting gas disposed in said tank; said gas having a predetermined density; a switch mounted in said tank having separable contacts and means for operating said contacts between open and closed positions; a sealed bellows means mounted in said tank adjacent to said operating means; a gas disposed in said bellows having a pressure-temperature relationship for a constant volume of gas substantially the same as the gas in said tank; the density of the gas in said bellows being equal to the density of the gas in the tank when the bellows is normally compressed whereby a predetermined loss of gas from the tank or a leak in said bellows will efiect expansion of the bellows; and means carried by the bellows to engage the operating means of said switch to prevent its operation when the bellows is expanded.

5. An enclosed circuit interrupter, comprising: a sealed tank; circuit interrupter means disposed in said tank; an arc interrupting gas disposed in said tank said gas having a predetermined density; said interrupter means having separable contacts and means for operating said contacts between open and closed positions; a sealed bellows means mounted in said tank adjacent to said operating means; a gas disposed in said bellows having a pressure-temperature relationship for a constant volume of gas the same as that of the gas in said tank; the density of the gas in said bellows being equal to the density of the gas in the tank When the bellows is normally compressed whereby a predetermined loss of gas from the tank or a leak in said bellows will effect expansion of the bellows independently of said operating means; and means actuated by the bellows to engage the said operating means to prevent its operation when the bellows is expanded.

References Cited by the Examiner UNITED STATES PATENTS 2,911,492 11/59 Beatty 200148 X FOREIGN PATENTS 512,623 9/39 Great Britain.

BERNARD A. GILHEANY, Primary Examiner. ROBERT K. SCHAEFER, Examiner. 

1. AN ENCLOSED SWITCH, COMPRISING: A SEALED TANK; AN ARC INTERRUPTING GAS DISPOSED IN SAID TANK; A SWITCH MOUNTED IN SAID TANK AND INCLUDING SEPARABLE CONTACTS AND AN OPERATING MECHANISM FOR ACTUATING SAID CONTACTS BETWEEN OPEN AND CLOSED POSITIONS; A CLOSED EXPANSIBLE CHAMBER MEANS MOUNTED IN SAID TANK ADJACENT TO SAID OPERATING MECHANISM; A GAS DISPOSED IN SAID CHAMBER HAVING A PRESSURE-TEMPERTURE RLATIONSHIP FOR A CONSTANT VOLUME OF GAS SUBSTANTIALLY THE SAME AS THAT OF SAID GAS IN SAID TANK; THE DENSITY OF THE GAS IN SAID CHAMBER BEING EQUAL TO THE DENSITY OF THE GAS IN SAID TANK WHEN THE EXPANSIBLE CHAMBER MEANS IS NORMALLY COMPRESSED WHEREBY A PREDETERMINED LOSS OF THE GAS FROM THE TANK OR A LEAK OF THE GAS FROM SAID CHAMBER WILL EFFECT EXPANSION OF SAID CHAMBER MEANS INDEPENDENTLY OF SAID OPERATING MECHANISM; AND MEANS CARRIED BY SAID CHAMBER MEANS FOR PREVENTING OPERATION OF THE SWITCH OPERATING MECHANISM WHEN THE CHAMBER IS IN THE EXPANDED CONDITION. 